Side-by-side electrodes have been proposed using a fluid bed electrode into which a second electrode is inserted, the second electrode being coated with an insulating material, e.g., polypropylene, of sufficient porosity to provide current flow while avoiding shorting of the cell. Various embodiments of side-by-side electrodes are disclosed in the literature.
In an article entitled "A Preliminary Investigation of Fluidized Bed Electrodes" by J. R. Backhurst el at (Journal of the Electrochemical Society [Electrochemical Technology]; Nov., 1969, pp. 1600-1607), a cell with a side-by-side electrode is disclosed for use in the cathodic reduction of the organic compound nitro benzene sulfonic acid to metanilic acid in aqueous sulfuric acid, a typical cell comprising a cathode bed of copper powder in a cathode chamber isolated by a porous diaphragm which in turn is surrounded by an annular anode (e.g., a lead anode) to provide a cell having a concentric configuration. In cathodically reducing the organic compound, copper-coated glass particles of 450 to 520 micron size were employed, the fluidized bed volume ranging from about 5% to 25% greater than the static bed volume.
In a paper entitled "Feasibility Study On The Electrowinning of Copper With Fluidized-Bed Electrodes" by J. A. E. Wilkinson et al (Institute of Mining and Metalurgy [London]; Sept. 1972, Vol. 81, pp. C157-C162), a fluidized-bed electrode is disclosed for the electrowinning of copper from leach liquors and other solutions. A side-by-side configuration proposed comprised anode and cathode compartments separated by a non-porous ion exchange membrane, the cathode comprising the fluidized bed. The results indicated that copper could be deposited from dilute solutions.
Another paper of interest is one entitled "The Fluidized Bed in Extractive Metallurgy" by D. S. Flett (Chemistry and Industry; Dec. 16, 1972, #24, pp. 983-988). In this paper, a side-by-side electrode configuration is disclosed comprising a vertical cell in which a fluidized bed is supported vertically on one side of the cell by a membrane and in which a vertically disposed anode is spaced to one side of the membrane-supported fluid bed. The electrolyte is fed from a leach circuit to the fluidized cathode cell for the recovery of metal values therefrom.
A number of cell configurations are considered in the paper entitled "Feasibility Study On The Electrowinning of Copper With Fluidized-Bed Electrodes" by J. A. E. Wilkinson et al (Institute of Mining and Metallurgy [London]; Vol. 82, pp. C199-C125, 1973). One arrangement comprises a side-by-side electrode configuration formed of concentric anode and cathode compartments. In this configuration, the cathode feeder which is tubular is embedded in the bed such that part of the bed is shielded from the anode which is not desirable.
In U.S. Pat. Nos. 3,941,669 and 3,951,773 assigned to Noranda Mines Limited, a fluidized bed electrode system is disclosed comprising an electrode chamber having a porous bed, a main electrode consisting of a bed of electrically conductive particles, an auxiliary electrode (i.e., an anode) with the surface thereof partially impregnated with a synthetic organic fiber screen cloth so that the auxiliary electrode can be introduced into the fluidized bed without risk of forming a short circuit, a current feeder extending into the bed, means for feeding a fluidizing gas into the bed of particles, and means for feeding solution through the fluidized bed.
U.S. Pat. No. 3,988,221 discloses the use of a cathodic fluid bed for the electrolytic removing of heavy metal ions from solution. The cell employed uses a centrally disposed anode with a permeable coating thereon so that the anode can penetrate the fluid bed without shorting the cell.
It would be desirable to provide a relatively high capacity fluid bed electrode system utilizing a cell having a plurality of anode-cathode chambers for use in extracting nickel from laterite leach solutions which normally contain less than about 10 grams per liter (gpl) of nickel and up to about 1 gpl cobalt. It would also be desirable to provide a fluid bed electrolyte cell for effecting separation of nickel and cobalt from fairly concentrated nickel solutions, for scavenging nickel and cobalt from ion exchange feed solutions, or even to remove impurities from nickel leach solutions, such as Cu, Cd, Zn, and the like.